Page 29 - Volume 2,Issue 2, July 2009

1

Laboratory of Pesticide Residues, Department of

Pesticides Control and Phytopharmacy, Benaki Phy-

topathological Institute, 8, St. Delta str., GR-145 61, Ki-

fissia (Athens), Greece.

Corresponding author:

C.Anagnostopoulos@bpi.gr

Hellenic Plant Protection Journal

2: 75-90, 2009

A multiresidue method for analysis of 56 pesticides in peaches

using liquid chromatography with tandemmass spectrometry

detection

C.J. Anagnostopoulos

1

, G.E. Miliadis

1

,

K.S. Liapis

1

and P. Aplada-Sarlis

1

Summary

A liquid chromatography–tandem mass spectrometry (LC–MS/MS) multiresidue method

for the simultaneous analysis of 56 multiclass pesticides and their metabolites in peaches is presented.

Pesticide residues were extracted from the samples with acetone and a mixture of dichloromethane/

light petroleum ether (50:50 v/v) and the determination was performed by liquid chromatography–

electrospray ionization–tandem mass spectrometry (LC-MS/MS), in a single chromatographic run. The

analytical performance was demonstrated by the analysis of blank peach samples spiked at three con-

centration levels, 0.01, 0.05 and 0.5 mg/kg, for each pesticide or metabolite. Good sensitivity and selec-

tivity of the method were obtained with limits of quantification of 0.01 mg/kg in most cases. The ma-

jority of the pesticides and their metabolites gave recoveries within the range of 65.7–125.3%, with rel-

ative standard deviations lower than 20%, for all concentration levels. Pesticide residues were found in

five out of the 14 samples. However, in most cases, the concentrations of the analytes found in the sam-

ples were lower than the MRLs established at the time of the analysis by the European Union.

Additional keywords:

acetone-based extraction method, LC–MS/MS, multiclass pesticides, validation

methods. Numerous different organic sol-

vents and mixtures of organic solvents have

been used to extract a wide range of pes-

ticides with different physicochemical prop-

erties from foods. Nowadays, the solvents

most commonly used for multiresidue anal-

ysis of pesticides are acetonitrile, acetone

and ethylacetate. Each solvent has some ad-

vantages and disadvantages in terms of se-

lectivity and convenience. Since the 1980s,

we have applied an acetone-based extrac-

tionmethod that is amenable to all our chro-

matographic separation systems (4).

Acetone is the least toxic, least expen-

sive and the most volatile of the three sol-

vents most commonly used in multiresidue

methods (acetone, ethyl acetate and ace-

tonitrile) (1). Acetone is completely miscible

with water allowing a good penetration in

the aqueous part of the crop. However, to

induce a distinct separation from the water

phase, acetone essentially needs addition of

a non-polar solvent, which leads to dilution

and lower recoveries of more polar analytes

(11). One of the most popular extraction

Introduction

The protection of crops against pests and

diseases by various, mostly synthetic pesti-

cides is a common approach in convention-

al farming. Even when pesticides are ap-

plied in accordance with good agricultural

practices (GAP), they can leave residues on

plants. Screening for residues in matrices,

such as cereals, requires analytical methods

with effective extraction, followed by a spe-

cific final determination step (15). Analytical

methodologies employed must be capable

of measuring residues at very low levels and

must also provide unambiguous evidence

to confirm both the identity and the con-

centration of any residue detected (7).

The choice of the solvent(s) for extrac-

tion is one of the most crucial decisions to be

made when developing new multiresidue